One possible reason could be that in the fanfiction, Kakashi might have made a decision during a mission that Naruto strongly disagreed with. For example, Kakashi could have chosen to sacrifice something important to Naruto in order to achieve the overall mission objective.
It could also be that in the fanfiction, Kakashi has some secrets that when revealed, make Naruto feel betrayed. For instance, if Kakashi was somehow involved with an enemy in a way that Naruto finds unacceptable, it would definitely cause Naruto to hate him. This would completely shatter Naruto's trust in Kakashi.
Maybe in this fanfiction, Kakashi has been acting differently from how Naruto expected. Naruto is used to seeing Kakashi as a certain kind of person, but if Kakashi starts to change his behavior, like being overly strict or cold towards Naruto without proper explanation, it could lead to Naruto hating him.
One possible reason could be that Naruto might feel Kakashi is too strict with his training. Maybe Kakashi's methods are too harsh for Naruto, making him frustrated and gradually developing dislike.
One reason might be that he doesn't like how fanfiction can change the relationships between characters. For example, in the original, his relationship with Naruto is based on training and mentorship, but fanfiction could make it something completely different.
One possible reason could be that he's had a bad experience with the taste. Maybe the ramen was made wrong one day and it left a really bad impression on him.
Perhaps in this fanfiction's universe, Naruto's goals and ideals are completely different from Kakashi and Sakura's. Naruto may be aiming for a more radical change in the ninja world, while Kakashi and Sakura are more conservative. Their differences could lead to Naruto developing a sense of hatred towards them as they constantly oppose his ideas.
Another reason might be related to their different ideologies within the ANBU. Naruto may have believed in a more collaborative and friendly approach within the organization, while Sasuke might have been more focused on individual achievement and power. This fundamental difference could lead to Naruto hating Sasuke in the fanfiction.
One possible reason could be jealousy. Maybe Naruto has some special abilities or a prophecy surrounding him that makes his family members, who might be less favored, jealous. For example, if there's a prophecy that Naruto will be the most powerful ninja in the village, his siblings or parents might envy that future for him and start to hate him out of their own insecurities.
It could also be due to a misunderstanding. Kakashi might be keeping some secrets from Naruto, like information about his parents or some hidden power within him. Naruto, being curious and eager for answers, could misinterpret Kakashi's motives for secrecy as a sign of distrust or dislike, which then turns into hatred.
One possible reason could be jealousy. Maybe his brother has some special abilities or gets more attention that Naruto feels he should have. For example, if his brother is really good at a certain jutsu and is always praised for it while Naruto struggles, that could lead to resentment.
Perhaps he thinks fanfic undermines the integrity of the original Naruto story. The official story has a certain narrative and character development, and fanfic can deviate from that significantly. When it comes to his connection with Naruto, any deviation in fanfic might be seen as a negative. For example, if a fanfic changes the way he mentors Naruto, it could be something he wouldn't like.
Maybe in this fanfic, the author wants to create a unique and dark plot. Kushina might be made to hate Naruto due to some kind of misunderstanding. For example, she could be misled to believe that Naruto has some connection to a great evil that she is against.